Robert McKillop

A new case takes Ludwig on a walking tour of Cambridge, where he’s faced with an impossible question. Meanwhile, Lucy goes undercover and makes a grim discovery of her own.

On a mission to crack the code in his twin’s notebook, John returns to the police station. A frustrated Lucy takes matters into her own hands and plays detective herself.

Puzzle setter John ‘Ludwig’ Taylor’s life is upended when his identical twin, DCI James Taylor, disappears. John reluctantly assumes his identity in order to track him down.